package com.jbm.jbmsupplier.util;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;

import android.os.NetworkOnMainThreadException;

public class GuidCreatorUtil {
    /** 
     * The value before MD5 
     */  
    private String valueBeforeMD5 = "";  
      
    /** 
     * The value after MD5 
     */  
    private String valueAfterMD5 = "";  
      
    /** 
     * The Random object to generate random number. 
     */  
    private static Random myRand = null;  
      
    /** 
     * To generate random number with security. 
     */  
    private static SecureRandom mySecureRand = null;  
  
    /** 
     * The id of localhost. 
     */  
    private static String s_id = "";  
      
    /** 
     * The flag. 
     */  
    private static final int PAD_BELOW = 0x10;  
      
    /** 
     * The flag. 
     */  
    private static final int TWO_BYTES = 0xFF;  
  
    /** 
     * Static block to take care of one time secureRandom seed. It takes a few 
     * seconds to initialize SecureRandom. You might want to consider removing 
     * this static block or replacing it with a "time since first loaded" seed 
     * to reduce this time. This block will run only once per JVM instance. 
     */  
    static  
    {  
        mySecureRand = new SecureRandom();  
        long secureInitializer = mySecureRand.nextLong();  
        myRand = new Random(secureInitializer);  
          
        try  
        {  
            InetAddress address = InetAddress.getLocalHost();  
            if (null != address)  
            {  
                s_id = address.toString();  
            }  
        }  
        catch (UnknownHostException e)  
        {  
            e.printStackTrace();  
        }  
        catch (NetworkOnMainThreadException e)  
        {  
            e.printStackTrace();  
        }  
        catch (Exception e)  
        {  
            e.printStackTrace();  
        }  
    }  
  
    /** 
     * Default constructor. With no specification of security option, this 
     * constructor defaults to lower security, high performance. 
     */  
    public GuidCreatorUtil()  
    {  
        getRandomGUID(false);  
    }  
  
    /** 
     * Constructor with security option. Setting secure true enables each random 
     * number generated to be cryptographically strong. Secure false defaults to 
     * the standard Random function seeded with a single cryptographically 
     * strong random number. 
     */  
    public GuidCreatorUtil(boolean secure)  
    {  
        getRandomGUID(secure);  
    }  
  
    /** 
     * Method to generate the random GUID 
     */  
    public void getRandomGUID(boolean secure)  
    {  
        MessageDigest md5 = null;  
        StringBuffer sbValueBeforeMD5 = new StringBuffer(128);  
  
        try  
        {  
            md5 = MessageDigest.getInstance("MD5");  
        }  
        catch (NoSuchAlgorithmException e)  
        {  
            e.printStackTrace();  
        }  
  
        try  
        {  
            long time = System.currentTimeMillis();  
            long rand = secure ? mySecureRand.nextLong() : myRand.nextLong();  
              
            sbValueBeforeMD5.append(s_id);  
            sbValueBeforeMD5.append(":");  
            sbValueBeforeMD5.append(Long.toString(time));  
            sbValueBeforeMD5.append(":");  
            sbValueBeforeMD5.append(Long.toString(rand));  
  
            valueBeforeMD5 = sbValueBeforeMD5.toString();  
            md5.update(valueBeforeMD5.getBytes());  
  
            byte[] array = md5.digest();  
            StringBuffer sb = new StringBuffer(32);  
            for (int j = 0; j < array.length; ++j)  
            {  
                int b = array[j] & TWO_BYTES;  
                if (b < PAD_BELOW)  
                {  
                    sb.append('0');  
                }  
                  
                sb.append(Integer.toHexString(b));  
            }  
  
            valueAfterMD5 = sb.toString();  
  
        }  
        catch (Exception e)  
        {  
            e.printStackTrace();  
        }  
    }  
  
    /** 
     * Convert to the standard format for GUID (Useful for SQL Server 
     * UniqueIdentifiers, etc. Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6 
     */  
    @Override  
    public String toString()  
    {  
        String raw = valueAfterMD5.toUpperCase();  
          
        StringBuffer sb = new StringBuffer(64);  
        sb.append(raw.substring(0, 8));  
        sb.append("-");  
        sb.append(raw.substring(8, 12));  
        sb.append("-");  
        sb.append(raw.substring(12, 16));  
        sb.append("-");  
        sb.append(raw.substring(16, 20));  
        sb.append("-");  
        sb.append(raw.substring(20));  
  
        return sb.toString();  
    }  
}
